1. Field of the Invention
The present invention relates to a safety device for an automobile vehicle. More particularly, this invention relates to a safety device for an automobile vehicle, such as an air bag or the like, which is as adapted as to protect a driver and a passenger at the time of a collision such as a car crash by operating the safety device at an appropriate timing.
2. Description of the Related Art
Recently, there is the increasing tendency for automobile vehicles to be provided with a safety device that is operated at the time of a collision, such as a car crash or the like, in order to protect a driver and a passenger. The safety devices include, for example, an air bag that is arranged to inflated in car compartment at the time of a collision and a pretension-type seat belt that is designed so as to become in a tension state or in a pulled state at the time of a collision.
Such safety devices, however, are required to-be operate with the highest certainty at the time of a collision which damages the vehicle body and causes the driver or the passengers to be injured to a severe extent. However it is not required to operate at the time of a collision which does not cause the driver or the passengers injury or in which a portion of the vehicle body such as a bumper is damaged and destroyed to some extent.
In order to satisfy these requirements, proposals have been made to have automobile vehicles provided with a means for deciding a timing of operating a safety device by computing an output signal generated from a G sensor at the time of a collision or an acceleration sensor mounted to the vehicle body.
For example, Japanese Patent Unexamined Publication (kokai) Nos. 3-148,348 and 3-114,944 propose that an output signal generated from the G sensor at the time of a collision is subjected to integration and the integrated value is compared with a predetermined value. More specifically, a decision is made to determine if the safety device is to be operated by determining the necessity of operation of the safety device on the basis of the state of the collision or an impact energy at the time of the collision, as indicated by the value obtained by the integration of the output value therefrom.
In order to offer appropriate protections to the driver and the passengers by operating the safety device for the automobile vehicle, it is desired that the safety device is arranged to operate at an appropriate time. For instance, it is required that the safety device should operate at the timing earlier when the car has collided head-on with another car or the like at such a high speed as likely to severely injure the driver or the passenger. Further, for example, it is desired that the safety device should operate at a relatively late or delayed time when the car has collided with another car or the like to such an extent as damaging a portion of the vehicle body yet not likely causing driver nor passenger injury at all or severe injury.
When an integration means is set to integrate the output signal generated from the G sensor in order to satisfy the requirement for operating the safety device at a late or somewhat delayed, time, on the one hand, it should be noted that it may become difficult to sufficiently satisfy the requirement for operating the safety device at an immediate time as when the strong and rapid output signal has been generated from the G sensor. When the integration means is set to integrate the output signal from the G sensor in order to comply with the requirement for operating the safety device at an earlier time, on the other hand, it may become difficult to satisfy the requirement for operating the safety device at a late or delayed time to a sufficient extent.